This application, and the innovations and related subject matter disclosed herein, (collectively referred to as the “disclosure”) generally concern systems for inferring a relative orientation of an apparatus from observations of an acoustic signal. More particularly but not exclusively, some disclosed principles are embodied as an audio device configured to detect a nearby, acoustically reflective surface, such as, for example, a nearby wall, book case, or shelf, from observed impulse responses to emissions from the audio device. The inferred orientation information can be used to affect a mode of operation of the device. For example, the orientation can be input to an acoustic beam former or other audio renderer to tailor the acoustic device's output to an in situ listening environment. Other examples include, but are not limited to, tailoring a video projector's projection direction relative to the inferred orientation, communicating orientation information over a communication connection, and issuing an alert in a user- or machine-readable form.
Known media systems, such as, for example, televisions, video projectors, loudspeaker cabinets, and sound processors require some degree of manual input or adjustment to establish, for example, a desired sound field corresponding to the media systems's environment. An audio processor can cause a given media system (or loudspeaker transducer therein) to emit a tone during a user-initiated calibration (e.g., during initial setup or after moving the media system). A microphone transducer can provide to an audio processor an observed frequency response to the emitted tone. The observed frequency response generally corresponds to the system through which the emitted tone passes. Based on the observed frequency response, the sound processor can alter, or adjust or otherwise “tune,” an acoustic signal provided to the loudspeaker in an attempt to render audio playback in a desired fashion.
However, conventional approaches to pursuing a desired sound field suffer several deficiencies. For example, many users dislike manually tuning their audio systems. As well, many users lack a separate microphone suitable for providing a frequency response to an audio processor. And, loudspeaker response characteristics tend to drift over time and in response to changes in temperature, requiring further manual tuning to correct. Still further, a change in a tuned loudspeaker's position can change the response characteristics and require a revised tuning, or calibration, of the audio renderer to achieve a desired response or sound field. Further, using an artificial tone to tune a loudspeaker interrupts a user's enjoyment of the loudspeaker because it prevents playing desired audio media during tuning procedures.
Thus, a need exists for an audio system to automatically infer its position and/or orientation in relation to its environment. A need also exists for an audio system to assess its tuning from time to time to account for changes in loudspeaker output characteristic and/or position. A need also exists for an audio system to assess or to change its tuning during playback of desired acoustic signals (e.g., during media playback, also sometimes referred to as “nominal playback”) to reduce or minimize disruption to a user's listening experience.